Hi, I am doing a review and hopefully meta-analysis for my Master thesis but I have the following problems:
- Some studies only give the difference between end trial and baseline data and other ones give mean and SD for baseline and end trial data. I thought to do it with the last one, but by doing it, I will let so many studies out of the meta-analysis. It is better to calculate all differences and do it with it?
- There are some studies that give the median and IQR. Can I do something to transform it to mean and SD? or the only options is to write the authors?
I already wrote to the corresponding authors but I did not get an answer.
Thanks in advance for the help, this is the first time doing a meta-analysis
you can combine all mean difference data, whether from matched or independent group studies.
there are other RG links to estimating mean/SD from median / IQR
see these links
https://www.researchgate.net/post/Is_there_any_way_to_get_mean_and_SD_from_median_and_IQR_interquartile_range
https://www.meta-analysis.com/downloads/Meta-analysis%20Effect%20sizes%20based%20on%20means.pdf
Yes, you can. Please visit the below link for more information.
https://training.cochrane.org/handbook/current
https://training.cochrane.org/handbook/current/chapter-10
Hi. You can legitimately pool the mean difference data with the endline data, and you may do further subgrouping to prevent confusion. As per Cochrane Handbook:
"When combining the data authors must be careful to use the appropriate means and standard deviations (either of final measurements or of changes from baseline) for each study. Since the mean values and standard deviations for the two types of outcome may differ substantially it may be advisable to place them in separate subgroups to avoid confusion for the reader, but the results of the subgroups can legitimately be pooled together."
Furthermore, you may convert median with IQR to mean with SD. Median = mean, SD = IQR/1.35. This is appropriate if the sample size is large and the data is normal.
You may find these in the Cochrane Handbook which is readily available online.
Louella Patricia D. Carpio Md. Obaidur Rahman James Leigh thank you all for your answers and your time!
I will check all the linke.
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